Dog Owner's Home Veterinary Handbook.pdf - Mr. Walnuts

C h a p t e r
THE EYES
The eye is an organ with several parts, each uniquely adapted to meet the special
needs of the dog. The eyeball is seated in a bony socket and protected by
a cushion of fat. Muscles surrounding the eyeball close the eyelids tightly in
response to pain, irritation, and objects approaching the eye. This makes it
difficult to inspect the surface of the eye for injuries and foreign bodies.
The large, clear window at the front of the eye is the cornea. Bordering it is
a narrow rim of white connective tissue called the sclera, which is much less
conspicuous in dogs than it is in humans. The sclera surrounds and supports
the entire eyeball. In certain breeds the sclera may be pigmented or spotted.
The round opening at the center of the eye is the pupil. Around the pupil is
a sphincterlike muscle called the iris. Like a shutter on a camera, the iris opens
and closes to regulate the amount of light that enters the eye. The iris contains
the pigment that gives the eye its color. While most dogs have eyes that are a
shade of brown, blue eyes are normal for some breeds and colors and have normal
vision. In some Northern breeds and dogs with the merle pattern, odd eyes
(one brown and one blue) are not uncommon.
A pinkish membrane called the conjunctiva covers the white of the eye
and doubles back to cover the inner surface of the eyelid. This membrane
contains blood vessels and nerve endings. When inflamed, the conjunctiva
appears red and swollen.
The eyelids are tight folds of skin that support the front of the globe.
Eyelashes are always present on the upper eyelids, but not on the lower eyelids.
There are small hairs on the edge of the lower lids.
The dog has an important third eyelid, the nictitating membrane, located
at the inner corner of the eye. This third eyelid is normally inconspicuous, but
when it extends across the surface of the eye, it looks as if the eyeball has
rolled back into its socket.
Tears are secreted by the lacrimalglands. Each eye has two lacrimalglands:
one beneath the bony ridge at the top of the eye socket and the other incorporated
into the third eyelid. Tears are conveyed to the surface of the eye by
small ducts that empty behind the lids. Tears prevent the cornea from drying
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